Congenital myasthenia and LEMS are potentially lethal disorder, which, even with careful management, significantly impedes participation in normal daily functions. Currently approved therapies have had little impact on promoting a normal quality of life activity in these patients. The goal is to systematically examine the effect of 3,4-DAP on the natural course of this disease and to gain additional experience in titrating 3,4-DAP with other available therapies to maximize clinical function and development in this patient population.